python 中的时间模块time

在Django的学习过程中的时间处理过程中遇到了strftime函数，于是结合《python cookbook》和python docs 对time模块中常用的一些操作和函数做了一点总结和归纳。

• time.time()

代表了从特定时间点，也被称作纪元（epoch：[英] [ˈi:pɔk] [美] [ˈɛpək, ˈiˌpɑk] ）开始所经历的秒数，是一个看起来不够直观的浮点数，这个时间根据不同的平台有所不同，一般为1970年1月1日午夜。例：

>>> import time
>>> time.time()
1299080804.953
>>> print time.asctime(time.gmtime(0))
Thu Jan 01 00:00:00 1970

• time.gmtime([secs]),  time.localtime([secs])

time.gmtime将任何时间戳（参数secs所代表的秒数）转化为一个元组，该元组为GMT（格林威治标准时），亦即UTC（世界标准时间）。也可以传递一个时间戳（从纪元开始经历的秒数）给time.localtime，会根据当前时区进行时间转化。

>>> time.gmtime(0)
time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=3, tm_yday=1, tm_isdst=0)
>>> time.localtime(0)
time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=8, tm_min=0, tm_sec=0, tm_wday=3, tm_yday=1, tm_isdst=0)

• time.asctime([t])

将struct_time转换为一个由24字符组成的字符串（24-character string），格式如：

 

Thu Mar 03 00:16:04 2011

• time.strftime(format[, t])

将一个元组（tuple）或者struct_time类，即参数t，转换为指定格式的字符串

• time.striptime(string[, format])

跟time.strftime相反的操作，解析给定的字符串并返回一个struct_time类。例：

>>> from time import strftime, gmtime
>>> strftime("%a %d %b %Y  %H:%M:%S")
'Thu 03 Mar 2011  00:29:41'
>>> strftime("%a %d %b %Y  %H:%M:%S", gmtime())
'Wed 02 Mar 2011  16:30:09'
>>> time.strptime("30 Feb 11", "%d %b %y")
...
ValueError: day is out of range for month
>>> time.strptime("28 Feb 11", "%d %b %y")
time.struct_time(tm_year=2011, tm_mon=2, tm_mday=28, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=0, tm_yday=59, tm_isdst=-1)

• time.sleep(secs)

 可以实现在python程序中的延时，单位为秒，并支持浮点数非整数秒的延时。例：

>>> for i in range(3):
    time.sleep(2.5)
    print "hello world!"

    
hello world!
hello world!
hello world!
>>> 

附一：struct_time

Index	Attribute	Values
0	tm_year	(for example, 1993)
1	tm_mon	range [1, 12]
2	tm_mday	range [1, 31]
3	tm_hour	range [0, 23]
4	tm_min	range [0, 59]
5	tm_sec	range [0, 61]; see (1) in strftime()description
6	tm_wday	range [0, 6], Monday is 0
7	tm_yday	range [1, 366]
8	tm_isdst	0, 1 or -1; see below

附二：directives can be embedded in the format string

Directive	Meaning	Notes
%a	Locale’s abbreviated weekday name.
%A	Locale’s full weekday name.
%b	Locale’s abbreviated month name.
%B	Locale’s full month name.
%c	Locale’s appropriate date and time representation.
%d	Day of the month as a decimal number [01,31].
%H	Hour (24-hour clock) as a decimal number [00,23].
%I	Hour (12-hour clock) as a decimal number [01,12].
%j	Day of the year as a decimal number [001,366].
%m	Month as a decimal number [01,12].
%M	Minute as a decimal number [00,59].
%p	Locale’s equivalent of either AM or PM.	(1)
%S	Second as a decimal number [00,61].	(2)
%U	Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.	(3)
%w	Weekday as a decimal number [0(Sunday),6].
%W	Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0.	(3)
%x	Locale’s appropriate date representation.
%X	Locale’s appropriate time representation.
%y	Year without century as a decimal number [00,99].
%Y	Year with century as a decimal number.
%Z	Time zone name (no characters if no time zone exists).
%%	A literal '%' character.

参考：1. python cookbook

        2. docs：http://docs.python.org/library/time.html#time.struct_time